Means for preventing voltage fluctuations in distributing-circuits



L. W. THOMPSON. MEANS FOR PREVENTING VOLTAGE FLUCTUATIONS IN DISTRIBUTING CIRCUITS.

APPLICATION FILED MAYl8|'l9l8.

1,373,922. Patented Apr. 5, 1921.

Inventor: Lows W.Thc mpson,

UNITED STATES PATENT OFFICE.

LOUIS W. THOM PSON, OF SCHENECTADY, NET]? YORK, ASSIGNOR TO GENERAL ELEC- TRIC COMPANY, A CORPORATION OF NEW YORK.

IEANS FOR PBEVET'I'TIN'G VOLTAGE FLUCTUATIONS IN DISTRIBUTING-CIRCUITS.

To all whom it may cmwem:

Be it known that I, LOUIS W. THOMPSON, a citizen of the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful Improvements in Means for Preventin Voltage Fluctuations in Distributingircuits, of which the following is a specification.

My invention relates to means for preventing objectionable volta e variations in a circuit from which a loa requiring substantially uniform voltage is energized when supplied from the same direct current source as a circuit from which a load drawing a variable current is, energized, and particularl' to means for preventing objectionable vo tage variations on lighting circuits which are supplied with current from the same direct current source as motor circuits.

The object of my invention is to prevent objectionable variations in the voltage in a circuit, from which a load requiring substantially uniform voltage is' energized,

upon variations in the current in a circuit,

from-which a load drawing a variable currentis energized, when both circuits are supplied with current from the same direct current source. In distribution systems wherein both a circuit, from which a load requiring substantially uniform voltage is energized, and a clrcuit, from which a load drawing variable current is energized, are connected to the same direct current source, which may comprise one or more generators, sudden changes of sufficient magnitude in the current in the latter circuit will cause objectionable variations in the voltage impressed upon the former circuit by said source. If the former circuit be employed to ener 'ze a lamp load comprising incondescent amps, which are sensitive to voltage changes, objectionable lamp flicker will occur. If the latter circuit be connected to elevator motors and the former circuits be connected to a lamp load the flickering will be especially pronounced and objectionable. The variation in the voltage of the source upon sudden variations in the current drawn therefrom is caused mainly by the inability of the generator or generators constituting the source to respond instantly to the varying current demands and to their inability to develop the same terminal voltage at all loads.

, Specification of Letters Patent.

Application filed May 18, 1918. Serial No. 235,250.

Patented Apr. 5, 1921.

The inability of the generator, or generators, constituting the source of direct current to respond instantly to varying current is energized, and which induce voltages in the former circuit to compensate substantially for variations in the impressed voltage which are caused by current variations in the variable load circuit.

In those systems in which the variation in the terminal voltage develo ed by the enerator or generators with di erent loads is objectionable, I may also employ automatic means for regulating the generator voltage. It is necessary that the action of the regulating means shall be rapid and sensitive in order that the voltage variations essential to their operation shall not in themselves result in objectionable fluctuations in the voltage of the circuit whose volta e should remain constant. To this end l preferably employ automatic voltage regulating means comprising a counter electromotive machine connected in the exciting circuit of the generator and vibratory means for controlling the electro-motive force of said machine.

Other objects and features of my invention will hereinafter appear.

My invention maymost readily be explained by referring to the single feature of the accompanying drawing in which 1 denotes a lighting clrcuit towhich a lamp load 2 may be connected by means of a switch 3. 4 denotes a motor circuit to which one or more motors 5 ma be connected by means of switches 6. i denotes transforming means comprising a core 8 of magnetic material having an air ga and a device 9 for adjustin the size of t e gap. The core 8 is provi ed with a plurality of windings 10, 11,'and 12. 13 and 14 denote direct current supply mains, the former of which is connected to one side of each of the circuits 1 and 4 and the latter of which is connected to the windin 10 which is included in circuit 1 and to t e winding 11 which is in- 16, a series field winding 17, and a shunt field winding 18. The transforming means 7 functions, in a manner hereinafter more fully described, to prevent fluctuations in the voltage of the circuit 1 of a magnitude and duration to cause objectionable flickering of the lamps when sudden changes of considerable magnitude occur in the load on the circuit 4. I preferably employ in combination with the generator 25 automatic voltage regulating means which are describedand claimed in my co-pending application Serial No. 221,046, filed, March 7, 1918. These means comprise a counter electromotive force machine 19 having an armature 20, connected in series with the shunt field winding 18 of the generator 25, a main field winding 21, a differential field winding 22, a vibratory device 23, and a dynamic brake 24. The vibratory device 23 responds to the variations in the voltage across the mains 13-14 to control the excitation of the field winding 21 of the counter electromotive force machine 19. The differential field winding 22 is connected in shunt to the series field winding 17 of the generator 25. The brake 24 is connected to oppose the rotation of the armature 20. These automatic voltage regulating means function in a manner hereinafter more fully described to cause the. generator to develop substantially the same predetermined voltage at all loads.

7 The operation of my invention, as at present understood, is as follows:

Assume the generator '25 to be in operation and the automatic voltage regulating means to be operating as hereinafter described, to cause the voltage across the mains 13-14 to have substantially the same pre determined voltage at all loads.

Now assume the switch 3 to be closed. The lamp load will then be energized from the circuit 1 with a voltage having a predetermined value. If now the current drawn by the motor circuit 4 be caused to vary suddenly to a sufficient degree due to the connection or disconnection of one or more of the motors 5, or to any other cause, the voltage across the main 13-14 will vary. If

. the current drawn by the circuit 4 increase,

the voltage across the mains 13-14 will de crease, and if the current drawn by the circuit 4 decreases, the voltage across the mains 13-14 will increase. In both casesthe variation inthe voltage of the mains-13-14 will in the lighting circuit 1 upon variations in the current in the motor circuit 4. By adjusting the impedance 15 inthe circuit of Y the winding 12, the magnitude, duration, and phase relation of said induced voltages may bemade to have the proper relation to v said current changes to compensate substantially for the variations in the voltage impressed upon the circuit 1 by the supply mains 13-14 occasioned by such current changes. Among other efiects, it will be understood that the winding 12 controls the rate of change of flux through the windings 10 and 11 upon a variation in the current in winding 11. The air, gap in the core 8 increases the reluctance of the magnetic path and by adjusting the device 9 the reluctance and the flux density may be varied. The air gap in the core 8 also causes the flux in the core to follqw more closely the variations in the magnetomotive forces of the windings thereon. The regulating means for the generator, althon h incapable of preventing variations in the voltage 13-14 upon sudden vagiations of considerable magnitude in the current demanded therefrom, nevertheless [operates to restore quickly the voltage across the mains 13-14 to a predetermined value after load changes occur. The vibratory device 23 responds to small changes in the voltexcitation of the main field winding 21 of the counter electromotive force machine 19, thereby controlling the counter electromotive force developed in the armature 20 and consequently the current in the 'field winding 18 and the voltage of the generator 25. The difi'erential field winding 22 of the counter electromotive force machine 19 responds to changes in current in the series field winding 17 of the generator 25. These automatic voltage regulating means are especially suited for the purposes of my invention because of their sensitiveness to very slight changes in the voltage of the mains 13-14 and their quickness of action. The differential field winding 22 a$istsin the attainment of these desirable characteristics since variationsjin the current out ut of the generator 25 vary through their influence on winding 22 the excitation of the generator 25 in a direction tending to maintain the voltage of said generator at the desired predetermined value.

'hile I have herein shown and described one modification of my invention. I do not desire to be limited to the exact arrangement shown and described but seek to cover in the appended claims all those modifications which come within the true spirit and scope of my invention.

'hat I claim as new and desire to secure by Letters Patent of the Ynited States, is

1. In combination. a source of direct current. a circuit from which a load drawing a variable current. is energized. a circuit from which a load requiring substantially uniform voltage is energized. means for connecting said source-to said circuits. an inducing winding located in the first mentioned circuit. an induced winding located in the second mentioned circuit, and means associated with said circuits for effecting such a rate of change of flux in said induced winding upon variations in the current in said inducing winding that voltage impulses of the proper kind to compensate substantially for variations in the. voltage impressed upon the second mentioned circuit by said source caused by variations in the current in the first mentioned circuit are developed in said induced winding.

2. In combination. a source of direct current. a circuit from which a load requiring substantially uniform voltage is energized, a circuit from which a load drawing variable current is energized. means for connecting said source to said circuits. and means for inducing voltages in the first mentioned circuit in response to variations in the second mentioned circuit comprising a magnetic core provided with a winding connected in the first mentioned circuit, a winding con nected in the second mentioned circuit. and means for controlling the rate of change of flux in said cure.

In combination. a source of direct current. a circuit from which a load requiring substantially uniform voltage is energized, a circuit from which a load drawing a variable current is energized. means for connecting said source to said circuits. and means for inducing voltages in the first mentioned circuit in response to variations in the current in the second mentioned circuit comprising a magnetic core provided with a winding connected in the first mentioned circuit. a winding connected in the second men tioned circuit, and a winding for controlling the rate of change. of flux in said core.

I. In combination, a sourceof direct current. a circuit from which a load requiring substantially uniform voltage is energized, a circuit from which a load drawing a variable current is energized, means for connecting said source to said circuits, and means for inducing voltages in the first mentioned circuitin response to variations in the current in the second mentioned circuit com prising a magnetic core provided with an air gap and a plurality of inductively related windings. one of which is located in the first mentioned circuit, another of which is located in the second mentioned circuit, and another of which is arranged to control the relation of the voltages induced in said first mentioned circuit to the current changes in said second mentioned circuit. and means i for adjusting the controlling action of the lastmentioned winding.

5. In combination, a source of direct current, a motor circuit, a lighting circuit, means for connecting said source to said circuits, and means responsive to variations in the current in said motor circuit for inducing voltages in said lighting circuit. said means comprising a magnetic core provided with an adjustable air gap and a plurality of ii'idnctively related windings. one 01 which is located in said motor circuit. another of which is located in said lighting circuit. and-another of which is located in a circuit comprising means for adjustably controlling the relation of electromotive force and current therein.

6. In combination. a direct current generator, regulating means for controlling the excitation of said generator, a circuit from which a load requiring substantially constant. voltage is energized. a circuit from which a load drawing variable current is energized. means for connecting said generator to said circuits, and means responsive to variations in the current in the latter cir cuit for inducing voltages in the former cir cuit comprising a magnetic core provided with a plurality of inductively related windings. one of which is located in the first mentioned circuit. another of which is located in the second mentioned circuit. and means for controlling the rate of change of flux in said core.

In witness whereof. I have hereunto set my hand this 16th day of May, 1918.

LOUIS W. THOMPSON. 

